I get tired of the ultra shallow, only one eye in focus, super wide aperture shot. Not to speak heresy, but if you routinely stop down a bright lens to get a workable DOF, are you not better off using a 2.8 lens or even an f/4 and shooting it wide open?

From a bokeh standpoint that is. Not all lenses have rounded aperture blades, but even with them aren't you still seeing little septagons or hexagons, etc. around highlights? Wide open (at whatever aperture that is for the lens) you get circles, at least in the center. You can still blur the background if you use a distant background and get in a bit close to subject, use telephoto, etc.

Well my personnal point is to still go for wide 1.2 1.4 open is the framing.

To be a little more explicit: yeah, shoulder shot with one eye in focus is a tired style IMHO but if you work from a bit further, you can get a nice full body shot or torso shot with the full subject(s) in focus and all the rest of the scene in bokeh.

In the spirit of the old school prefocusing, my prefered working distances:- on a 85 1.2, wide open, at 10 meters you have 50cm in front and behind. Very good 1 subject torso shot situation. http://500px.com/photo/39910852 At 15 meters you have 1 meter in front and one meter behind the focus point. Generally good for full body shots or sitting subjectS. Very easy to have several poeple included without the usual default of one personn OOF (saw that yesterday in a pro press shot, ewwwww). - on a 35 1.4, wide open, at 5 meters you have 70cm in front and close to a meter in the back. Perfect for full body shot in a average environment that you want to exist but oof. http://500px.com/photo/39910846

In short, keep doing maths and get good at estimating distances and very wide aperture become more than a 1 eye focus machine.

In short, keep doing maths and get good at estimating distances and very wide aperture become more than a 1 eye focus machine.

+1.... Maths is key... There is actually an app for that on your phone... you tell it your camera, lens, shooting dist etc and it will tell you the depth of the focal plane... i played with it until i got a feel for my lenses.

In short, keep doing maths and get good at estimating distances and very wide aperture become more than a 1 eye focus machine.

+1.... Maths is key... There is actually an app for that on your phone... you tell it your camera, lens, shooting dist etc and it will tell you the depth of the focal plane... i played with it until i got a feel for my lenses.

Math is always nice, but these calcs are actually physics! Maths does not deal with such... "applicable" problems

To the OP's question, I think that the extent of OOF blur would be the same for a (as example) 50 mm 1.2 stopped down to 2.8 and a 50 mm 2.8 at 2.8. Bokeh is not about the extent but rather about the quality of the OOF blur. I think that that is not related to the max aperture* but to the design of the optical path and the shape of the iris.

*as a general statement, one could assume that with expensive large aperture lenses more attention has been given to the quality of the OOF blur (e.g. number and shape of aperture blades). So a 50 1.2 will (likely) give a more smooth blur than a 50 2.8. This generalisation is ofcourse not always true; a 24-70 2.8 ii gives a very nice bokeh, much nicer I think than a stopped down nifty fifty.

If you tried to compare, say 24 1.4L stopped down to f2.8, to 16-35 2.8L zoom to 24mm wide open (I have both and did similar comparsion), the 24L will give you more and better looking background blur.

Reason? Optical vignetting. An f1.4 lens stopped down to f2.8 will have it's optical vignetting almost all cleared up. Compared to the f2.8 lens wide open at it's worst. The results is center looks similar, going towards the edge and corner the f2.8 lens progressively lose brightness and the amount of blur it can achieve.

It's same as stating that when f2.8 lens is at wide open, it's corners might only give you brightness and blur of a f5.6 lens!

The quality of out of focus areas is utterly unique for each lens design. No two brands of 70-200/2.8 will offer the same results. Simular maybe, but not the same. With a stopped down prime, the aperture blade design will be the biggest desciding factor to bokeh smoothness. I have seen some really clunky aperture blades on lenses which claim to be "perfectly round when stopped down" and I've see great ones too. With a wide open zoom, the aperture blades are wide open and the internal structure of the lens will influence the Bokeh...which is usually round and very clean. With a stopped down aperture blades, the shape influencing the bokeh is pretty uniform around the image, but with a wide open lens, the internal barrel sometimes causes the bokeh to look like cats eyes around the edages of the frame. It's up to you to descide which is the better option for you and your intended photograph.